Conventional reel mower cutting units are used on golf courses and other turf areas that require grass to be cut very accurately. The cutting units are typically rolled across the surface of the ground by a powered vehicle. These cutting units include a generally cylindrical reel that has a plurality of blades which rotate in close proximity to a stationary bedknife fixed with the frame of the cutting unit. Grass is cut by a shearing action between the bedknife and the rotation blades of the reel. The height at which grass is cut can be adjusted by altering the height at which the cutting unit frame is positioned above the ground surface. The bedknife is routinely serviced and adjusted to be in proper position with respect to the reel blades such that the grass is cut effectively. Conventional cutting units provide a linkage that allows an operator to adjust the position of the bedknife with respect to the reel blades.
Examples of linkages for adjusting bedknives are shown in U.S. Pat. No. 5,822,966 assigned to Textron Inc. and U.S. Pat. No. 6,044,637 assigned to Deere & Company. Adjustment of the bedknife may be needed because the reel wears and decreases in diameter over time. For example, wear may be due to field conditions or accepted maintenance procedures including sharpening. On many reel mowers, one may adjust the bedknife by rotating the bedknife assembly on a pivot axis to maintain the cutting surface of the bedknife in close proximity to the reel. The pivot axis may be defined by bushings that are rigidly mounted to the mower frame. Pivot shoulder bolts are mounted the bedknife support or shoe, and freely rotate within the bushings to allow the bedknife assembly to be rotated and adjusted to the reel.
In many cases, if a cutting reel becomes increasingly worn and its diameter is reduced, further adjustment of the bedknife may cause the non-cutting rear surface of the bedknife to drag on the turf. In other words, adjustments cause the bedknife to rotate so that the bedknife's non-cutting rear surface drops below the cutting edge. Dragging the rear surface of the bedknife can be a serious problem, especially in areas where a low height-of-cut is demanded. For example, some golf course greens may require a height-of-cut of about three millimeters.
Dragging the bedknife is unacceptable because it can damage the turf. Before that occurs, the reel may need to be replaced so that the bedknife may be rotated back to an acceptable position. Replacing the reel is costly and labor intensive. For that reason, it would be desirable to increase the adjustment range of the bedknife, to permit continued adjustment of the reel-to-bedknife gap after the cutting blades are worn and the reel diameter is reduced. It would be desirable to allow continued adjustment of the bedknife without dragging the bedknife on the turf. It would be desirable to extend the useful life of a cutting reel by adjusting the pivot axis of the bedknife assembly.